The present invention relates generally to fiber optic communications and, more particularly, to high speed data links for use with light modulation systems including a superconductive plate assembly in a data transmission scheme.
The light modulation system as disclosed in U.S. Pat. No. 5,768,002 is capable of transmitting optical data signals at high data rates such as, for example, rates of terabits per second (Tbit/s) at a given wavelength over a single optical fiber. For example, the light modulation system can be used in a wavelength-division multiplexing (WDM) system to provide the optical data signal at a WDM channel.
However, in order to achieve a complete data link capable of handling optical data signals at a single wavelength at Tbit/s rates, an optical receiver in the data link must be able to detect the optical data signals at Tbit/s rates. Such an optical receiver singly capable of detecting Tbit/s optical data signals of a single wavelength is not commercially available at the present time to the applicant""s knowledge. Although optical detectors capable of detecting optical signals at a rate of 750 GHz or with response times on the order of picoseconds or less are known in the art, these devices are still in their experimental stages hence are not yet commercialized.
Prior art data links have not had to deal with this problem of the unavailability of Tbit/s rate optical receivers because light modulation systems capable of transmitting optical data signals at Tbit/s rates at a given wavelength are not currently known at this time to the applicant""s knowledge, with the exception of the light modulation system disclosed in U.S. Pat. No. 5,768,002. Existing high speed light modulation systems generally consist of a series of N light modulators, each light modulator corresponding to one channel out of N channels and producing optical data signals at rates of less than Tbit/s at a unique wavelength corresponding to a particular WDM channel out of a range of wavelengths xcex1xe2x88x92xcexN. The multitude of optical data signals over the range of wavelengths, each optical data signal having its own unique wavelength, are multiplexed onto an optical fiber. The multiplexed signal is received by a demultiplexer which separates the multiplexed signal into the separate optical data signals according to wavelength. The separated optical data signals are then detected by a plurality of optical detectors, each operating at less than Tbit/s rates.
The prior art data link as a whole can be made to transmit data at Tbit/s rates by using a plurality of data sources, optical sources and optical detectors all operating at Gbit/s rates. For example, if a hundred optical sources are provided (i.e., N=100), with each optical source generating an optical signal at 10 Gbit/s and at a distinct wavelength out of the wavelength range xcex1 through xcex100, then the aggregate optical data rate is one Tbit/s. Following transmission through an optical fiber, a WDM multiplexer combines the one hundred optical signals such that the resulting multiplexed signal contains all optical signals of the wavelength range xcex1 through xcex100. The WDM demultiplexer then separates the multiplexed signal into distinct wavelengths to be detected by a hundred optical detectors, each detector operating at 10 Gbits/s. As a result, it is possible to transmit data using the prior art data link at an aggregate rate of 1 Tbit/s.
It is submitted, however, the aforedescribed prior art data link has a number of disadvantages. In order to increase the total data transmission rate of the prior art data link above approximately 1 Tbit/s, the number of channels, and hence the number of data sources and optical sources used in the data link, must be increased. This condition may be satisfied by narrowing the wavelength differences between channels thus fitting more channels into a given wavelength range xcex1 through xcexN and/or widening the wavelength range between xcex1 and xcexN. However, narrowing the wavelength differences between the channels increases the probability of data transmission error due to potential optical signal overlap and crosstalk and puts a greater demand on the WDM demultiplexer to accurately separate the optical signals into the distinct wavelengths. As is well known in the art, there is only a finite range available for use as the wavelength range xcex1 through xcexN, outside of which significant optical signal loss occurs due to the material properties of the optical fiber as well as other components of an optical communication system, such as repeaters and amplifiers. Therefore, the wavelength range cannot be widened indefinitely using currently available technology, hence it is difficult to increase the number of channels to increase the data transmission rate. Furthermore, increasing the number of different wavelengths traveling simultaneously through the optical fiber also increases the probability of occurrence of undesired, nonlinear optical effects during transmission. Care must be taken to avoid such nonlinear optical effects, thus adding to the overall complexity and cost of this prior art data link at faster data transmission rates. Still further, WDM channels require a guard band on either side of the specific channel wavelength in order to reduce wavelength overlap and crosstalk between channels. Since no data can be transmitted on the guard band, the wavelengths used in the guard band are essentially wasted bandwidth.
The present invention provides a high speed data link which serves to resolve the problems described above with regard to prior art data links in a heretofore unseen and highly advantageous way and which provides still further advantages.
As will be described in more detail hereinafter, there is disclosed herein a high speed data link including a transmitting arrangement having a transmitter output. The transmitting arrangement includes a source of light having a certain wavelength. The transmitting arrangement further includes a layer of superconductive material through which the light from the source must pass before the light can reach the transmitter output. The superconductive material is switchable between a superconducting state in which,the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. Still further, the transmitting arrangement includes an arrangement for switching the superconductive material between its superconducting and non-superconducting states to provide a train of light pulses having the certain wavelength and containing optical data. The transmitting arrangement further includes a wavelength changing device, which is optically coupled to the layer of superconductive material, for changing the wavelength of the light pulses and providing a train of wavelength changed light pulses containing optical data at the transmitter output. The high speed data link also includes an optical fiber, one end of which is optically coupled to the transmitter output, for directing the train-of wavelength changed light pulses away from the transmitting arrangement. Additionally, the high speed data link includes a receiving arrangement optically coupled to an opposing end of the optical fiber. The receiving arrangement includes an all-optical demultiplexer for dividing the train of wavelength changed light pulses into a series of sub-trains of wavelength changed light pulses. The receiving arrangement further includes a series of optical receivers, each optical receiver being designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses.
In another aspect of the invention, the transmitting arrangement of the high speed data link includes a series of light modulating devices for generating a series of trains of light pulses over a specified range of wavelengths. Each light modulating device has a light output and provides at its output one of the trains of light pulses, and the light pulses of each train of light pulses have an assigned wavelength out of the specified range of wavelengths. Each light modulating device includes a source of light having a given wavelength and a layer of superconductive material through which the light from the source must pass before the light can reach the light output of that light modulating device. The superconductive material is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. Each light modulating device further includes an arrangement for switching the superconductive material between its superconducting and non-superconducting states to provides a train of light pulses having the given wavelength and containing optical data. In addition, each light modulating device includes a wavelength changing device, optically coupled to the layer of superconductive material, for changing the wavelength of the light pulses from the given wavelength into the assigned wavelength and providing a train of wavelength changed light pulses containing optical data at the light output such that no two light modulating devices in the series of light modulating devices generate trains of light pulses at the same assigned wavelength out of the specified range of wavelengths. The transmitting arrangement further includes a WDM multiplexer optically coupled to the light outputs of the series of light modulating devices for reading the series of trains of wavelength changed light pulses in parallel and combining the series of trains of wavelength changed light pulses into a multiplexed signal at the transmitter output of the transmitting arrangement. An optical fiber, one end of which is optically coupled to the transmitter output, directs the multiplexed signal away from the transmitting arrangement. The high speed data link further includes a receiving arrangement including a WDM demultiplexer, optically coupled to an opposing end of the optical fiber, for receiving the multiplexed signal and separating the multiplexed signal back into the series of trains of wavelength changed light pulses. Further, the receiving arrangement includes a series of light receiving devices configured to receive the series of trains of wavelength changed light pulses. Each of the receiving arrangements is optically coupled to the WDM demultiplexer and is designed to receive at least one of the trains of wavelength changed light pulses of a particular wavelength out of the specified range of wavelengths. Moreover, each of the receiving arrangements includes an all-optical demultiplexer for dividing the train of wavelength changed light pulses into a series of sub-trains of wavelength changed light pulses. Additionally, each of the receiving arrangements further includes a series of optical receivers, each of which is designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses.
In still another aspect of the invention, a method for providing a high speed data link is disclosed. Accordingly, a train of light pulses containing optical data is transmitted. In this transmitting step, light having a certain wavelength is generated and directed onto a layer of superconductive material, which is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. The superconductive material is switched between its superconducting and non-superconducting states for generating a train of light pulses having the certain wavelength . The wavelength of the light pulses is then changed to provide a train of wavelength changed light pulses containing optical data. The train of wavelength changed light pulses is directed to a desired location then received at the desired location and divided into a series of sub-trains of wavelength changed light pulses. Additionally, the series of sub-trains of wavelength-changed light pulses are detected using a series of optical receivers, each of which is designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses.
In yet another aspect of the invention, an alternative method for providing a high speed data link is disclosed. Accordingly, a multiplexed signal containing optical data is transmitted. In this transmitting step, light of a given wavelength is generated and directed onto a layer of superconductive material, which is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. The superconductive material is switched between its superconducting and non-superconducting states for generating a train of light pulses having the given wavelength and containing optical data. The wavelength of the light pulses is changed from the given wavelength to an assigned wavelength out of a specified range of wavelengths. The steps of light generation, switching of the superconductive material and wavelength changing are repeated to provide a series of trains of wavelength changed light pulses, each of which trains of wavelength changed light pulses contains optical data and has a distinct, assigned wavelength out of the specified range of wavelengths in such a way that no two trains of wavelength changed light pulses in the series of trains of wavelength changed light pulses have the same assigned wavelength out of the specified range of wavelengths. The series of trains of wavelength changed light pulses are read in parallel and combined into a multiplexed signal containing optical data. The multiplexed signal is directed to a desired location and received at the desired location where the received, multiplexed signal is separated back into the series of trains of wavelength changed light pulses. Each of the trains of wavelength changed light pulses is divided into a series of sub-trains of wavelength changed light pulses. The series of sub-trains of wavelength is detected using a series of optical receivers, each which is designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses of a particular, assigned wavelength out of the specified range of wavelengths.
In still yet another aspect of the present invention, an optical communication system for use with a communication satellite is disclosed. The optical communication system includes means for transmitting a train of light pulses containing optical data. Transmitting means has a transmitter output and includes a source of light having a certain wavelength and a layer of superconductive material through which the light from the source must pass before the light can reach the transmitter output. The superconductive material is switchable between a superconducting state in which the light cannot pass therethrough and a non-superconducting state in which the light can pass therethrough. Transmitting means also includes an arrangement for switching the superconductive material between the superconducting and non-superconducting states for providing a train of light pulses having the certain wavelength and containing optical data. Transmitting means also includes a wavelength changing device optically coupled to the layer of superconductive material for changing the wavelength of the light pulses and providing a train of wavelength changed light pulses containing optical data at the transmitter output. The optical communication system also includes means for directing the train of wavelength changed light pulses from the transmitter output to the communication satellite, which redirects the train of wavelength changed light pulses toward a desired location, and means for intercepting the train of redirected, wavelength changed light pulses from the satellite at the desired location. The optical communication system further includes means for receiving the train of redirected, wavelength changed light pulses intercepted by the intercepting means. Receiving means includes an all-optical demultiplexer for dividing the train of redirected, wavelength changed light pulses into a series of sub-trains of wavelength changed light pulses and a series of optical receivers, each of which is designed to detect at least one of the sub-trains of wavelength changed light pulses out of the series of sub-trains of wavelength changed light pulses.